1. Field of the Invention
The present invention relates to safety glass mirrors, particularly to laminated safety mirrors and glazing, and to methods of forming same.
2. Background of the Invention
Prior known laminated mirrors have had their mirror coatings located at the sides of the glass sheets opposite the bonding layers, because the bonding materials previously used have been incompatible with the silver coating and the protective paint applied over the silver. The result has been diminished brightness of the mirror image produced, due to the great thickness of glass and bonding layer through which light and images must pass. Also, the prior known laminated safety mirrors could not be offered in dual-sided form without making and then enclosing two single-sided safety mirrors in a frame, making them heavy and expensive.
Previous efforts to place the mirror coating adjacent the bonding layer have failed either because the bonding materials attacked the silver coating and the protective paint, reducing functionality and appearance of the mirror with black spots, discolorations, blemishes, and streaks, or because the protective paint attacked the bonding materials, causing delamination and failure to meet safety standards. These problems were significant deterrents, as they compromised the integrity of the product and thus prevented it from being offered as a durable safety material.
No solution has heretofore been found, despite great efforts in the architectural glass industry to do so. Interlayer bonding materials used adjacent the protective coatings on mirrored surfaces, including polyvinyl acetal resin and polyvinyl butyral resin, have been tested and rejected due to such chemical attack and/or deterioration that products made with them failed to meet safety standards. Other known bonding materials such as plasticized polyvinyl acetate, polyacrylic ester, cellulose acetate plastic, and cellulose nitrate adhered with gelatin have also been tried and abandoned due to moisture sensitivity, low temperature brittleness, color, and adhesion durability problems. Some polyurethane based adhesive bonding materials such as aromatic polyurethanes and hot melt urethane bonding materials are not light stable and are susceptible to becoming hazy or discolored under ultraviolet light. These products thus are ineffective as interlayer bonding materials for use in laminated safety glass adjacent the mirror coating and protective layer.
Prior U.S. patents addressing the laminated safety mirror and similar problems include U.S. Pat. No. 2,468,568, which discloses double and single mirrors including polyvinylbutryal or methyl methacrylate layers and bonding agents of resin, plastic, or gelatin, and U.S. Pat. No. 4,511,618, which discloses laminated reflective panels using thin foils bonded to glass using polyvinylbutryal medium, epoxy resins, silicone-based adhesives, unspecified polyurethane, and hot-melt adhesives.